Nanobiosensors based on individual olfactory receptors

The animal olfactory system represents the gold standard of biosensors, due to its ability to identify and discriminate thousands of odorant compounds with very low thresholds. Using olfactory receptors (ORs) as sensing elements instead of chemical sensors, biosensors would benefit the naturally optimized molecular recognition of odorants to develop a new generation of bioelectronic noses. The purpose of SPOT-NOSED European project was the development of nanobiosensors based on single ORs anchored between nanoelectrodes, to mimic the performances of natural olfactory system. Nanobiosensors arrays could then increase odorant sensitivity or widen the odorant detection spectrum. ORs were expressed in yeasts plasmic membrane, and their functionality tested in whole yeasts. Then, nanosomes bearing the ORs were prepared from S. cerevisiae, and Surface Plasmon Resonance was performed on nanosomes for quantitative evaluation of OR response to odorant stimulation. ORs retain full activity and discrimination power in immobilized nanosomes, thus allowing their use in the fabrication of the nanobiosensors. Nanoelectrodes were fabricated using conventional photolithography and focused ion beam milling, with sizes in adequation with the nanosomes. ORs borne by nanosomes were specifically immobilized onto conducting substrates via mixed Self Assembled Monolayers, neutravidin and specific antibody to the ORs. The process was optimized by microcontact printing, and the anchored nanovesicles visualized by Atomic Force Microscopy. A transimpedance preamplifier suited for low-noise wide-bandwidth measurements was designed to be directly connected to the nanoelectrodes. Electrochemical Impedancemetric Spectroscopy detected significant changes upon electrodes functionalization, grafting of ORs carried by nanosomes, and ORs conformational change induced by odorant binding.     

Iron complexes of dietary flavonoids: Combined spectroscopic and mechanistic study of their free radical scavenging activity

Combined spectroscopic (UV/visible, Raman, MS) and theoretical approaches were used to assess interaction of iron(III) with quercetin and baicalein in aqueous buffered solutions. Obtained results implicated formation of two iron quercetin complexes, with pH-dependent stoichiometries of 1:2 and 1:1, and one iron baicalein complex with stoichiometry of 1:1. Results of vibrational analysis and theoretical calculations implicated 3-hydroxy-4-carbonyl and the 3′-hydroxy-4′-hydroxy group of catechol as chelating sites for quercetin. For baicalein 5-hydroxy-6-hydroxy group is energetically the most favourable, although 5-hydroxy-4-carbonyl and 6-hydroxy-7-hydroxy chelating sites are energetically similar. Antiradical activity, reaction stoichiometry and number of inactivated DPPH molecules per mole of antioxidant indicated quercetin as a better antioxidant than its iron complex, baicalein and iron baicalein complex. The same structural features appeared to be important both in complexation and antioxidant activity. The equilibrium geometries, optimised using the B3LYP/6-31G (d, p) level of theory, predicted structural modifications between the ligand molecules in free state and in the complex structures. Correlation between experimental and theoretical results was very good.     

Influence of VO2 nanostructured ceramics on hydrogen desorption properties from magnesium hydride

The hydrogen desorption properties and kinetics of MgH₂–VO₂ composite prepared by mechanical milling of MgH₂ and VO₂ have been investigated. Structural characterization of produced nanocomposite was done by X-ray powder diffraction (XRD), particle size analysis and scanning electron microscopy (SEM). The structure and morphology of the composite have been correlated with hydrogen desorption properties investigated by differential thermal analysis (DTA). It has been shown that short mechanical milling of nanostructured VO₂ and MgH₂ leads to decrease of hydrogen desorption temperature of MgH₂ by 80 K. The mechanism of desorption has been changed from phase boundary reaction, spherical symmetry for untreated MgH₂ to phase boundary reaction, cylindrical symmetry for the composite material. The activation energy for desorption has been reduced by adding VO₂ ceramics as a catalyst.     

Electrochemical synthesis and corrosion behavior of polyaniline-benzoate coating on copper

Electrochemical polymerization of polyaniline (PANI) coating on copper electrode was performed galvanostatically in the current density range between 0.50 and 1.25 mA cm^?2, from aqueous solution of 0.3 mol dm^?3 sodium benzoate and 0.2 mol dm^?3 aniline. The corrosion behavior of PANI coated copper and copper electrode exposed to 0.5 mol dm^?3 sodium chloride solution was investigated by potentiodynamic and electrochemical impedance spectroscopy techniques. It was observed that thin PANI (5 μm) coating had provided efficient protection (～96%) to copper in 0.5 mol dm^?3 sodium chloride solution. Unusual initial impedance behavior to that normally observed with conventional organic coatings was attributed to dedoping of benzoate anions from the polymer coating.     

Evaluation of alginate hydrogels under in vivo–like bioreactor conditions for cartilage tissue engineering

Alginate hydrogels in forms of discs and packed beds of microbeads (~800 μm) were tested in a novel bioreactor at 10% strain using two regimes: at a loading rate of 337.5 μm/s and at sequential increments of 50 μm displacement every 30 min. Compressive strength increased with the increase in alginate concentration (1.5 vs. 2% w/w) and the content of guluronic residues (38.5 vs. 67%). Packed beds of microbeads exhibited significantly higher (~1.5–3.4 fold) compression moduli than the respective discs indicating the effects of gel form and entrapped water. Short-term cultivation of microbeads with immobilized bovine calf chondrocytes (1.5% w/w, 33 × 10⁶ cells/ml) under biomimetic conditions (dynamic compression: 1 h on/1 h off, 0.42 Hz, 10% strain) resulted in cell proliferation and bed compaction, so that the compression modulus slightly increased. Thus, the novel bioreactor demonstrated advantages in evaluation of biomaterial properties and cell-biomaterial interactions under in vivo–like settings.     

Variable neighbourhood decomposition search for 0–1 mixed integer programs

In this paper we propose a new hybrid heuristic for solving 0–1 mixed integer programs based on the principle of variable neighbourhood decomposition search. It combines variable neighbourhood search with a general-purpose CPLEX MIP solver. We perform systematic hard variable fixing (or diving) following the variable neighbourhood search rules. The variables to be fixed are chosen according to their distance from the corresponding linear relaxation solution values. If there is an improvement, variable neighbourhood descent branching is performed as the local search in the whole solution space. Numerical experiments have proven that exploiting boundary effects in this way considerably improves solution quality. With our approach, we have managed to improve the best known published results for 8 out of 29 instances from a well-known class of very difficult MIP problems. Moreover, computational results show that our method outperforms the CPLEX MIP solver, as well as three other recent most successful MIP solution methods.     

The simple one-step solvothermal synthesis of nanostructurated VO2(B)

VO₂(B) has been successfully synthesized by simple, facile and environmental friendly one-step solvothermal method using V₂O₅ and ethanol as a starting agent. Obtained micrometer-sized powder was composed from mutually welded nanosized rod-like, flat and snowflake structures. VO₂(B) powder was tested for possible application as anode material for aqueous lithium ion batteries. Lithium intercalation/deintercalation reaction has been carried out by cyclic voltammetry in a saturated aqueous solution of LiNO₃. At scan rate of 10 mV s^?1 very stable cyclic performance of such obtained VO₂ was established with discharge capacity around 184 mAh g^?1.